A Survey Of Impacts Of Pre-exposure Prophylaxis For HIV On Sexual Behavioral Patterns And Transmission Of HIV/STIs Among Men Who Have Sex With Men

Objective 1.To construct a mathematical model for the transmission of HIV and sexually transmtted infections(STIs)among men who have sex with men(MSM)worldwide and predict the epidemic in the future one year;2.To evaluate the impacts of HIV pre-exposure prophylaxis on HIV/STIs epidemics among MSM;3.To forecast the epidemics of HIV/STIs with various pre-exposure prophylaxis preventive schemes among MSM.Methods We searched literature and conducted a systematic review on the relationship between HIV/STIs prevalence and condom use.Through multiple ways,we obtained behavioural and epidemic parameters to construct mathematical model that calibrated to the epidemic trends of HIV/STIs among MSM worldwide.Using the Monte Carlo method to evaluate the uncertainty of the mathematical model,we forecasted the changes in HIV/STIs epidemic trends with current preventive approach and various hypothetical pre-exposure prophylaxis preventive intervention schemes and analyzed the impacts of a potential risk compensation from pre-exposure prophylaxis.We developed two preventive schemes,scheme one assumed 50% MSM taking antiretroviral drugs daily and 50% of them having anal sex without condom;Scheme two added HIV/STIs screening at a regular interval to MSM who taking drugs based on scheme one.We stratified the analysis by continents and region.Besides,we predicted and assessed the HIV/STIs epidemic trends in the future decade in the six countries that have already provided PrEP for MSM.Results 1.The established mathematical model accurately reflected the transmission patterns of the HIV/STIs epidemic among MSM.Mathematical model forecasts that if maintaining the current scale of HIV preventive measures,the HIV prevalence of MSM in the future one year will reach 0.91 [95% confidence interval(CI):(0.59-1.24)]/100 person-year,and the new infection among syphilis,gonorrhoea and chlamydia will be 3.30(2.21-4.44)/100 person-year,19.81(11.28-32.54)/100 person-year and 19.54(13.54-26.57)/100 person-year,respectively.2.HIV pre-exposure prophylaxis could significantly reduce HIV newly infections.In the presence of risk compensation,new HIV incidence would retain a declining trend,while STIs infection risk would increase.In scheme one,new HIV incidence would be 0.53(0.34-0.71)/100 person-year and new syphilis,gonorrhoea and chlamydia incidence would be 3.53(2.35-4.78)/100 person-year,22.36(12.64-36.98)/100 person-year and 21.50(14.83-29.27)/100 person-year;3.If taking antiretroviral drugs daily and also having HIV/STIs screening test regularly,HIV incidence would decrease more dramatically,and it would be 0.15(0.04-0.25)/100 person-year in one year whereas syphilis,gonorrhoea and chlamydia incidence would remain increasing within one year then after then decrease steadily,which would be 2.68(1.90-3.78)/100 person-year,15.78(8.36-28.17)/100 person-year and 14.78(9.83-21.03)/100 person-year in two year.4.In the six countries with existing pre-exposure prophylaxis,new HIV incidence would reduce close to zero and STIs newly infection would below 7/100 person-year in ten years.Conclusions Pre-exposure prophylaxis is not only as daily antiretroviral medication,but also should be a comprehensive HIV/STI prevention package incorporating HIV/STIs screening.